Archive for August, 2008

As I see it, the main contribution of C S Smith is in (a) drawing attention to the possible applications of topological ideas to metallurgical problems; (b) setting the grain growth problem as belonging to the same class as cell structures in biological tissues, soap froths, foams, and problems on space filling; and, (c) using models of soap froths as near exact geometric models of grain growth in metals.

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I just want to draw your attention to the reply that Smith gave to the discussions section, in which he expressed a hope and a word of caution:

The discussion by Dr. von Neumann is much appreciated, and his conclusions are as remarkable for their simplicity as they are nonobvious on first consideration of the problem. It is greatly to be hoped that he, or some other mathematician, will be able to deduce similar relations in three dimensions and can combine these with the topological requirements to give the equilibrium distribution of bubbles toward which a froth must tend.

… Metals are not soap bubbles, even though soap bubbles are so useful in illustrating the basic principles, as I hope I have demonstrated in the paper.

Coarsening and growth are not the only problems of interest when it comes to soap bubbles; in the latest issue of This week’s finds in Mathematical Physics, John Baez writes about a closely related problem, namely, the problem of chopping 3D space into equal volume cells with minimal surface area; Baez begins with the most recent ‘Water Cube’ building at Beijing Olympics 2008, and goes on to collect lots of references and web resources on The Kepler conjecture, The Honeycomb conjecture, and the Weaire-Phelan structure; along the way, he also has some interesting historical observations to make:

In his 1887 paper on this subject, Kelvin wrote:

No shading could show satisfactorily the delicate curvature of the hexagonal faces, though it may be fairly well seen on the solid model made as described in Section 12. But it is shown beautifully, and illustrated in great perfection, by making a skeleton model of 36 wire arcs for the 36 edges of the complete figure, and dipping it in soap solution to fill the faces with film, which is easily done for all the faces but one. The curvature of the hexagonal film on the two sides of the plane of its six long diagonals is beautifully shown by reflected light.

I think this is a nice passage. We may remember Kelvin for his profound work on electromagnetism and thermodynamics – or his 1900 lecture on two “dark clouds” hanging over physics: the Michelson-Morley experiment (which foreshadowed special relativity) and black body radiation (which foreshadowed quantum mechanics). We may not imagine him playing around with soap bubbles! But it shows that good science stems from curiosity, and curiosity knows no bounds.You can read Kelvin’s paper here:

His lively mind is evident from the selection of papers on this site. For example: “On Vortex Atoms”, where he unsuccessfully tried to build atoms out of knotted electromagnetic field lines, and wound up giving birth to knot theory. Some others I hadn’t heard of: “On the origin of life”, “The sorting demon of Maxwell”, and “Windmills must be the future source of power”.

A piece worth bookmarking and returning to often — for repeated readings and pointers to resources. Take a look!

PS: By the way, the C S Smith special issue of Resonance that I referred to in my grain growth post is also a nice place to read about some of this stuff — for example, it contains a piece by Denis Weaire himself. Have fun!

As I said, this was probably my favorite of the experiments that I did at NIST, because it was mine from start to finish. It was my off-hand idea to do the experiment in the first place, I made the decisions about what to measure, and I did almost all of the analysis myself.

This was also one of the first times I felt like a Real Physicist, because the analysis I was doing wasn’t trivial. I needed to figure out what the various bits of the signal meant before I could extract information from them, and while there weren’t any real “eureka!” moments, there were a lot of small epiphanies where things just clicked into place, and I realized what something meant, and how to use it to measure something interesting.

As I said, the whole thing was a blast, and is one of my fondest memories of grad school.

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Standard practice at PRL– thanks to Dan Kleppner, as I found out at DAMOP– is to send submitted articles out to two referees, and ask for feedback within two weeks. I checked the status of the article somewhat obsessively, of course, and saw that Referee A returned their report very quickly, while Referee B didn’t do anything until the two-week limit. A discreet day or so after the two-week deadline, I sent an email to the editors asking what was up, and the next day saw a status update saying that a reminder had been sent. A day or so after that, I saw the dreaded “Non-report communication received from Referee B.”

This generally means that a paper has been returned by the referee, saying that they were too busy to review it. That sends it back to the editors to choose another referee, and the two-week window resets.

So I was rather surprised to receive a notice from the editors the next day, saying that the article had been accepted on the strength of Referee A’s report only.

The report was included, but I’ve since lost the exact text. It was almost absurdly good, though– the referee, whoever it was, absolutely gushed about the paper, saying that it was “sure to be a seminal work” in the field.

My favorite line of the whole thing was a bit that went something like “The only thing I take issue with is the authors’ claim that many interesting issues remain to be resolved. It seems to me that this paper has completely covered everything.”

I have no idea who refereed it– the reports are anonymous, and they didn’t leave any obvious terminological clues (there’s some variance in the names of relevant quantities among research groups). As a couple of people observed at the time, I’d really like to be able to request that person as a referee for all my subsequent work.

Sadly, this didn’t really turn out to be a frequently-cited paper– the Abstract Data Service puts it at 16 citations, which sounds about right. The field as a whole really shifted away from cold collisions around that time, and there hasn’t been much done that would follow up on it. Still, having someone speak that highly of your work is just amazing. It was a great boost to my confidence heading into thesis writing and my trip to Japan in late ’98.

This was the part of my graduate career where I really got on a roll. Between July of 1997 to May of 1999, I was an author on two PRL’s and a Phys. Rev. A article, gave invited talks at a conference in Austria and the APS Centennial Meeting, spent three months in Japan, and completed my thesis. I also started dating Kate during that span (she was in DC working on Capitol Hill).

Be aware of the seven ways of not getting a PhD:· not wanting a PhD; · overestimating what is required; · underestimating what is required; · having a supervisor who does not know what is required; · losing contact with your supervisor; · not having a ‘thesis’ (i.e. position, argument) to maintain; · taking a new job before completing.

Work to understand the implications of these traps fully in your own situation and determine not to succumb to them.

Re-establish your determination regularly when blandishments to stray from your programme of work recur.

The link actually describes each of the ways in greater detail; take a look!

Via Literary Saloon, I learnt about this profile by Boyd Tonkin of P D James. It took time for me to begin appreciating James; but, once I got the hang of it, till now, very few are the instances in which she disappointed me. I did not have a word till now to describe why I like her novels so much (and, why I found it difficult to appreciate them in the beginning); the profile supplies me with one — micro-climate:

Every reader of PD James knows that institutions give rise to their own micro-climate, with local habits and habitats every bit as exotic as the seething life of a sheltered bay or a deep ravine. “I’m fascinated by organisations, the way in which people relate to each other at work,” says the perennial bestseller, who was already almost 20 years into an acclaimed career of crime when she retired from the civil service in 1979. From the NHS and the Home Office to the BBC (she served five years as a Governor) and the House of Lords (where she takes the Tory whip), she can underpin her detective fiction with wider inside knowledge than almost any author in the history of the genre. “Of course, it has been tremendously helpful to have had a bureaucratic life apart from the writing. I don’t think I’m the kind of writer who would do well sitting in a country cottage, frankly.”

Baroness James of Holland Park, a Londoner by choice if not by birth, does not sit in a country cottage and conjure up fantasy backdrops for the “contaminating” deaths that shake small worlds – from churches to publishers – to their roots in her novels. “When I see people who have got other jobs,” she explains, “I long to question them about how their day is organised; how they make their money; what are the problems, and so on.” All the same, the engine-room of her empire of mystery feels as if it stands at a slight angle to its place and time.

Almost every grad student struggles with the difficulty of explaining your dissertation topic to strangers (not to mention friends and family) without launching into an hour long lecture on the topic. One enterprising geographer has come up with a unique solution to the problem: write a comic book.

Ju Hui Judy Han at UC Berkely participated in the 24 hour comic day in 2006. The challenge was to write 24 pages in 24 hours. She chose to write about her dissertation. The result can be downloaded here (PDF) or viewed online.

I love the idea of saying, the next time someone asks you about your dissertation: “Here, read my comic book.”

I guess the only thing that is missing now is a Katha-Kalakshepam based on one’s thesis!

Magnetic senses are one of the most enigmatic of animal abilities. Among our fellow mammals, only a few rodents and one species of bat are known to use internal compasses. Some believe that horses, dolphins and whales use the same trick but that’s been very hard to prove. Large groups of these animals don’t lend themselves to careful laboratory experiments. Begali’s innovation was in using satellites to turn the entire planet into a natural laboratory. Now, it’s time for others to follow up on her results.

And the satellite based research that Yong is talking about is this:

For centuries, farmers have known that their livestock not only gather in large herds but also tend to face the same way when grazing. Experience and folk wisdom offer several possible reasons for this mutual alignment. They stand perpendicularly to the sun’s rays in the cool morning to absorb heat through their large flanks, or they stand in the direction of strong winds to avoid being unduly buffeted and chilled.

But cows and sheep don’t just line up during chilly spells or high wind. Their motivations for doing so during warm, pleasant and unremarkable weather, or indeed in the dead of night, have been a mystery until now. In a new paper, Sabine Begali from the University of Duisburg-Essen in Germany spied on aligned herds of cows and deer using satellite images from Google Earth.

The images revealed a striking behaviour that had been going unnoticed for millennia, right under the noses of herdsmen and hunters – their herds were lining up in a north-south line like a living compass needle. Influenced by a magnetic sense that has only just become apparent, their default point of reference is not the source of wind or the angle of the sun, but the Earth’s magnetic poles.

How do you look at a face? Since 1965 it has been a tenet of psychology that people look at faces through the triangle method; that is, they scan the eyes (especially) and then the mouth, in a basic visual process assumed to be common to all humans. But guess what? This conclusion was based on studies in which only Westerners participated. Now that someone has finally thought to study non-Westerners, you can consign the universality of facial processing to the scientific dustbin.

As scientists report today in the journal PLoS ONE, Westerners tend to look at particular features on a face, such as the eyes or mouth, while East Asians focus on the center of the face, which provides a more holistic view of all the features.

Anthropologist Michael Wesch gave a thoughtful and engaging talk on ‘An anthropological introduction to YouTube’ to the Library of Congress earlier this year and, rather appropriately, it’s available online as a video on the popular video sharing site.

Wesh runs a digital ethnography project which looks at how cultures form and operate on the net.

The project’s blog is also full of fascinating insights and is well worth checking out if you thought anthropology was only ever about people who don’t have electricity.

As many readers may already know, my good friend and fellow mathematical bloggerTim Gowers, having wrapped up work on the Princeton Companion to Mathematics (which I believe is now in press), has begun another mathematical initiative, namely a “Tricks Wiki” to act as a repository for mathematical tricks and techniques. Tim has already started the ball rolling with several seed articles on his own blog, and asked me to also contribute some articles. (As I understand it, these articles will be migrated to the Wiki in a few months, once it is fully set up, and then they will evolve with edits and contributions by anyone who wishes to pitch in, in the spirit of Wikipedia; in particular, articles are not intended to be permanently authored or signed by any single contributor.)

An interesting idea — I certainly would love to take a look at the wiki page once in a while!

An extreme example of a teaching style that is virtually orthogonal to what we Americans know is the one that has been attributed to the celebrated Hungarian analyst F. Riesz. He would come to class accompanied by an Assistant Professor and an Associate Professor. The Associate Professor would read Riesz’s famous text aloud to the class. The Assistant Professor would write the words on the blackboard. Riesz would stand front and center with his hands clasped behind his back and nod sagely.

In most of the educational institutions today, Assistant and Associate Professors might not render the same services that Riesz’ assistants and associates rendered him; however, the appellations remain; and very recently, one of my friends was complaining against them; I now see that FSP also has objections to these titles:

Let’s do away with the existing adjectives used to describe the professorial ranks. These terms are inaccurate, somewhat annoying, and they do not inspire confidence in our non-academic friends and relations. We need more awe-inspiring adjectives.

Even once you become a Professor (as in, a so-called “full” professor, although “full” is not technically part of the title) and you lose the demeaning adjectives, all is not perfect. When people ask me my title and I say “Professor”, I am then asked “What kind of professor? Do you have tenure?”, as if I am leaving out some information by not including any adjective. In some situations I am reluctant to say “full professor” because I am quite tired of the “full of what?” question that inevitably follows. We all need better adjectives.

As you may have seen, there is a new poll in the sidebar to the right. The poll will be live for a week. I suppose I can add to it if any new exciting nominations are made. The perceptive reader will note, on reading the poll list, that I have failed to come up with a serious list of viable alternatives, but went ahead with the poll anyway for its entertainment value (such as it is).

As I have been discussing this week (and a few other random times in the past), the motivation for this effort is the unsatisfactory nature of the current terms for professorial ranks. “Assistant Professor” is particularly annoying and kind of demeaning as a term, and “Associate Professor” isn’t much better.

Take a look and have fun — don’t foget to take a look at the comments!